/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.heartbeat;

import org.apache.flink.runtime.clusterframework.types.ResourceID;
import org.apache.flink.runtime.concurrent.ScheduledExecutor;

/**
 * Heartbeat monitor which manages the heartbeat state of the associated heartbeat target. The
 * monitor notifies the {@link HeartbeatListener} whenever it has not seen a heartbeat signal
 * in the specified heartbeat timeout interval. Each heartbeat signal resets this timer.
 *
 * @param <O> Type of the payload being sent to the associated heartbeat target
 */
public interface HeartbeatMonitor<O> {

	/**
	 * Gets heartbeat target.
	 *
	 * @return the heartbeat target
	 */
	HeartbeatTarget<O> getHeartbeatTarget();

	/**
	 * Gets heartbeat target id.
	 *
	 * @return the heartbeat target id
	 */
	ResourceID getHeartbeatTargetId();

	/**
	 * Report heartbeat from the monitored target.
	 */
	void reportHeartbeat();

	/**
	 * Cancel this monitor.
	 */
	void cancel();

	/**
	 * Gets the last heartbeat.
	 *
	 * @return the last heartbeat
	 */
	long getLastHeartbeat();

	/**
	 * This factory provides an indirection way to create {@link HeartbeatMonitor}.
	 *
	 * @param <O> Type of the outgoing heartbeat payload
	 */
	interface Factory<O> {
		/**
		 * Create heartbeat monitor heartbeat monitor.
		 *
		 * @param resourceID                 the resource id
		 * @param heartbeatTarget            the heartbeat target
		 * @param mainThreadExecutor         the main thread executor
		 * @param heartbeatListener          the heartbeat listener
		 * @param heartbeatTimeoutIntervalMs the heartbeat timeout interval ms
		 * @return the heartbeat monitor
		 */
		HeartbeatMonitor<O> createHeartbeatMonitor(
			ResourceID resourceID,
			HeartbeatTarget<O> heartbeatTarget,
			ScheduledExecutor mainThreadExecutor,
			HeartbeatListener<?, O> heartbeatListener,
			long heartbeatTimeoutIntervalMs);
	}
}
